This patent discloses an integrated system for demodulating the output of a quartz MEMS magnetometer of the type disclosed by U.S. patent application Ser. No. 14/628,182 filed Feb. 20, 2015 noted above. The disclosed quartz MEMS magnetometer utilizes the fact that frequency modulation (FM) of the quartz thickness shear mode oscillator is proportional to the strength of an external magnetic field. As such, a system can provide information regarding the strength of an external magnetic field, and several embodiments of such a system are disclosed herein.
The object of this invention is to detect or sense magnetic fields (which is known as magnetometry), especially magnetic fields sensed by a magnetometer of the types disclosed by U.S. patent application Ser. No. 14/628,182 filed Feb. 20, 2015 and entitled “A Micro-scale Piezoelectric Resonating Magnetometer” and U.S. patent application Ser. No. 14/997,160 filed on the same date as this application and entitled “Quartz Magnetometer having a Quartz Resonant Plate with a Broaden Distal End for Enhanced Magnetic Sensitivity”.
One application of magnetometry is electronic compassing (measuring Earth's magnetic field direction for use in a compass). The advantage of the current invention is that it describes a system which can be implemented using miniature components, preferably manufactured utilizing MEMS technology and ultimately miniaturized into a single compact system integrating a MEMS die and and application-specific integrated circuit (ASIC) die containing the system electronics. This disclosed system is inherently portable with resolution limits around 50 nanoTesla (nT). Embodiments of the system utilizing closed-loop operation and/or phase-sensitive detection enable even higher detection accuracy, improving the resolution to far below 50 nT are also described herein.